Additional methods that when implemented make an Android.Widget.IExpandableListAdapter take advantage of the Android.Widget.Adapter view type mechanism. Lists that contain different types of group and/or child item views, should use an adapter that implements this interface. This way, the recycled views that will be provided to IExpandableListAdapter.GetGroupView(int, System.Boolean, System.Boolean, System.Boolean) and IExpandableListAdapter.GetChildView(int, System.Int32, System.Int32, System.Int32, System.Int32) will be of the appropriate group or child type, resulting in a more efficient reuse of the previously created views.

An Android.Widget.IExpandableListAdapter declares it has one view type for its group items and one view type for its child items. Although adapted for most Android.Widget.ExpandableListViews, these values should be tuned for heterogeneous Android.Widget.ExpandableListViews.

[Android Documentation]